The simplifying expression “square lens”, for reasons of conciseness, is taken to mean in the context of the invention a lens which has at least one cylindrical face (input and/or output) with vertical generatrices. The contour of the lens is therefore not limited to the square shape, but may be rectangular, circular, oval, ovoid or ogival, or have a contour of the square or rectangular type but with rounded edges or bevels, or with any other contour.
A headlight comprising such a square lens is known from EP-A-1 243 846. This headlight has the advantage of a relatively shallow depth (that is to say dimension in the direction of the optical axis) and a high light flux. However, the range of the light beam is small. In addition, this headlight does not make it possible to easily produce a cut-off of the beam inclined to the horizontal, for example by 15°, in order to produce a dipped headlight.
The aim of the invention is in particular to provide a headlight which, whilst keeping a shallow depth and high light flux, makes it possible to obtain a long range of the beam and, if so desired, to produce a cut-off of the beam inclined to the horizontal, in particular for a dipped headlight function.